A 3-yr study evaluated the effect of planting date, variety and degree of ear maturation on maize weevil, Sitophilus zeamais (Motchulsky), colonization of corn in the field. Within each plot, paper bags were used to prevent oviposition during one of three consecutive 2-wk periods beginning at the 3/4-milk-line stage. Adult emergence from bagged ears was compared to that from unbagged ears. Maize weevil adults emerged from 15.6% of all ears tested. Numbers of adults emerging from infested ears ranged from 1 to 135 with a mean (±SE) of 11.9 ± 18.5. A greater percentage of Mycogen 7559 ears were infested than those of Pioneer 3167 or Pioneer 3146, and the infested Mycogen 7559 ears also supported the emergence of a greater number of adults. A significant planting date effect was found each year of the study, but the nature of that effect was not consistent. A significant planting date-by-year interaction may have been due to weather affecting the date maize weevils were available for colonization, or more likely, to interference from earlier planted corn near our plots that attracted the first overwintering weevils. Oviposition resulting in successful emergence was found to occur during all 3 of the 2 wk exclusion periods with the last period having the greatest impact on the percentage of infested ears and the second period having the greatest impact on the number of emerging weevils per 500 g of kernels.
3Department of Crop and Soil Sciences.